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[Clang][RISCV] Remove forced-sw-shadow-stack (#115355)

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This option was used to override the behavior of
`-fsanitize=shadowcallstack` on RISC-V backend, which by default use a
hardware implementation if possible, to use the software implementation
instead. After #112477 and #112478, now two implementation
is represented by independent options and we no longer need it.
This commit is contained in:
Jesse Huang
2024-11-08 13:46:27 +08:00
committed by GitHub
parent b613a54075
commit 3ad6403577
3 changed files with 4 additions and 15 deletions
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9
clang/docs/ShadowCallStack.rst
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@@ -59,11 +59,10 @@ and destruction would need to be intercepted by the application.
The instrumentation makes use of the platform register ``x18`` on AArch64,
``x3`` (``gp``) on RISC-V with software shadow stack and ``ssp`` on RISC-V with
hardware shadow stack, which needs `Zicfiss`_ and ``-mno-forced-sw-shadow-stack``
(default option). Note that with ``Zicfiss``_ the RISC-V backend will default to
the hardware based shadow call stack. Users can force the RISC-V backend to
generate the software shadow call stack with ``Zicfiss``_ by passing
``-mforced-sw-shadow-stack``.
hardware shadow stack, which needs `Zicfiss`_ and ``-fcf-protection=return``.
Users can choose between the software and hardware based shadow stack
implementation on RISC-V backend by passing ``-fsanitize=shadowcallstack``
or ``Zicfiss`` with ``-fcf-protection=return``.
For simplicity we will refer to this as the ``SCSReg``. On some platforms,
``SCSReg`` is reserved, and on others, it is designated as a scratch register.
This generally means that any code that may run on the same thread as code

4
clang/include/clang/Driver/Options.td
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@@ -4930,10 +4930,6 @@ def msave_restore : Flag<["-"], "msave-restore">, Group<m_riscv_Features_Group>,
HelpText<"Enable using library calls for save and restore">;
def mno_save_restore : Flag<["-"], "mno-save-restore">, Group<m_riscv_Features_Group>,
HelpText<"Disable using library calls for save and restore">;
def mforced_sw_shadow_stack : Flag<["-"], "mforced-sw-shadow-stack">, Group<m_riscv_Features_Group>,
HelpText<"Force using software shadow stack when shadow-stack enabled">;
def mno_forced_sw_shadow_stack : Flag<["-"], "mno-forced-sw-shadow-stack">, Group<m_riscv_Features_Group>,
HelpText<"Not force using software shadow stack when shadow-stack enabled">;
} // let Flags = [TargetSpecific]
let Flags = [TargetSpecific] in {
def menable_experimental_extensions : Flag<["-"], "menable-experimental-extensions">, Group<m_Group>,

6
clang/test/Driver/riscv-features.c
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@@ -29,12 +29,6 @@
// DEFAULT-NOT: "-target-feature" "-save-restore"
// DEFAULT-NOT: "-target-feature" "+save-restore"
// RUN: %clang --target=riscv32-unknown-elf -### %s -mforced-sw-shadow-stack 2>&1 | FileCheck %s -check-prefix=FORCE-SW-SCS
// RUN: %clang --target=riscv32-unknown-elf -### %s -mno-forced-sw-shadow-stack 2>&1 | FileCheck %s -check-prefix=NO-FORCE-SW-SCS
// FORCE-SW-SCS: "-target-feature" "+forced-sw-shadow-stack"
// NO-FORCE-SW-SCS: "-target-feature" "-forced-sw-shadow-stack"
// DEFAULT-NOT: "-target-feature" "+forced-sw-shadow-stack"
// RUN: %clang --target=riscv32-unknown-elf -### %s -mno-strict-align 2>&1 | FileCheck %s -check-prefixes=FAST-SCALAR-UNALIGNED-ACCESS,FAST-VECTOR-UNALIGNED-ACCESS
// RUN: %clang --target=riscv32-unknown-elf -### %s -mstrict-align 2>&1 | FileCheck %s -check-prefixes=NO-FAST-SCALAR-UNALIGNED-ACCESS,NO-FAST-VECTOR-UNALIGNED-ACCESS
// RUN: %clang --target=riscv32-unknown-elf -### %s -mno-scalar-strict-align 2>&1 | FileCheck %s -check-prefix=FAST-SCALAR-UNALIGNED-ACCESS